Six NATO troops were shot dead by a man wearing a border police uniform during a training exercise in eastern Afghanistan.
The incident appeared to be the latest in a string of recent attacks by renegade police and soldiers.
It shows the underlying pressure on NATO-led troops as they try to train Afghan forces rapidly to allow the handover of security responsibility from next year.
A statement said the person who shot the troops was also killed.
The six troops are thought to be American.
